JP6632128B2 - Method of designing container in liquid level reflection type tilt sensor, tilt sensor having the container, and method of producing tilt sensor having the container - Google Patents

Description

  The present invention relates to a liquid level reflection type tilt sensor, a method of designing a container for forming a free liquid surface of the sensor, a tilt sensor having the container, and a method of producing a tilt sensor having the container.

  Generally, a surveying instrument has a tilt sensor inside, and is leveled based on the detection result of the tilt sensor and adjusted to be in a horizontal attitude. As the tilt sensor, a liquid surface reflection type is often used. In the liquid-surface reflection type, a predetermined dark-field pattern is emitted from a light source and reflected on the surface of the liquid (free liquid surface). The reflected light is received by a light-receiving sensor, and the displacement of the light-receiving pattern (light-receiving image) is measured. To detect. For example, in Patent Literature 1, a dark field pattern formed by a one-dimensional slit is reflected on a free liquid surface, and the amount of movement is detected. In Patent Document 2, a pattern position is calculated from a pattern arrangement in which a dark-field pattern by a lattice-like two-dimensional slit is reflected on a free liquid surface, and the detection results of a light receiving sensor are added in an X direction and a Y direction.

JP-A-11-118482 JP 2007-127628 A

  The above-mentioned free liquid surface is formed by sealing a liquid having an appropriate viscosity in a cylindrical container with a lid. The size of the container must be large enough to allow a change in the liquid surface shape (meniscus) near the wall surface of the container. On the other hand, in recent years, there has been a demand for downsizing of the sensor, and a further reduction in the size of the container has been required. However, in the conventional method of designing a container shape, a container is actually created, a liquid is sealed therein, a light source light is applied to the container, an actual light receiving pattern is obtained, and the result is fed back to the design. The method was taken. In addition, since the liquid surface shape changes depending on the characteristics of the liquid to be sealed and the temperature conditions, it is necessary to repeat the above method under various conditions according to the specifications required for the sensor (temperature range in which the sensor is used). Was. Therefore, there is a problem that it takes time and cost to optimize the shape of the container.

  SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and an object of the present invention is to provide a liquid-reflection-type tilt sensor that can quickly and inexpensively obtain a container shape according to sensor specifications.

  In order to solve the above-mentioned problems, a method of designing a container of a liquid-surface reflection type inclination sensor according to an embodiment of the present invention is based on a Young-Laplace type and a hydrostatic pressure type. A liquid surface shape calculation step for determining the liquid surface shape of the liquid formed on the plate in the horizontal direction x and the vertical direction y, and receiving light reflected from a temporary mirror surface having the liquid surface shape by irradiating a dark field pattern from a temporary light source An optical simulation step of obtaining a pattern; and a container adjusting step of determining whether the image accuracy of the light receiving pattern satisfies a sensor accuracy requirement and adjusting the shape of a cylindrical container for enclosing the liquid. .

  In the above aspect, in the liquid surface shape calculation step, an actual contact angle θ1 of the liquid with respect to the container is obtained, and the angle between a first curve f1 representing the liquid surface shape and its y axis is the contact angle θ1. It is also preferable to include a second step of offsetting the y-axis in the x-axis direction to a certain position.

  In the above aspect, in the liquid surface shape calculation step, the first curve f1 is obtained from two directions of one wall surface of the container and the other wall surface opposite thereto, and a horizontal distance from the center of the container is X. It is also preferable to include a third step of obtaining a second curve f2 indicating the liquid level shape in the container with the liquid level height being Y.

  In the above aspect, it is preferable that the liquid surface shape calculation step further includes a fourth step of complementing a shape near X = 0 of the second curve f2 with a polynomial.

  In the above aspect, in the container adjusting step, the optical simulation step is performed assuming a length of the container in the X direction while fixing a light beam diameter of light source light incident on the container, and an image of the light receiving pattern is formed. It is also preferable that when the accuracy satisfies the sensor accuracy requirement, the length of the container in the X direction is reduced, and when the accuracy is not satisfied, the length of the container in the X direction is increased.

In the above aspect, in the container adjustment step, the length of the container in the X direction is fixed, and the optical simulation step is performed assuming a light beam diameter of light source light incident on the container, and an image of the light receiving pattern is formed. It is also preferable that the diameter of the light beam is expanded when the accuracy satisfies the sensor accuracy requirement, and the diameter of the light beam is narrowed when the accuracy is not satisfied.

  In the above aspect, the maximum value Ymax of the Y value of the second curve f2 is obtained, and the height h of the container is set to be equal to or greater than the value obtained by adding the maximum value Ymax to the height h ′ of the horizontal liquid surface of the liquid. It is also preferable to include a container height designing step for designing.

  Further, in the liquid-surface reflection type tilt sensor according to an aspect of the present invention, a light source, a collimating lens for collimating a light beam from the light source, and light from the collimating lens are incident, and the contrast can be recognized by image analysis. A dark-field pattern, a beam splitter that directs light passing through the dark-field pattern to a free liquid surface, a focus lens that collects light from the beam splitter, a liquid that forms the free liquid surface, and the liquid The dark field pattern is applied to the temporary mirror surface formed by the liquid surface shape of the liquid, which is enclosed and is formed on an infinitely wide plate perpendicular to the horizontal liquid surface from the Young Laplace formula and the hydrostatic pressure formula. A cylindrical container having a horizontal length designed to minimize the image accuracy of the light receiving pattern obtained by satisfying the sensor accuracy requirement, and light reflected from the free liquid surface A light receiving element for receiving, and having an a processing unit for analyzing the received image of said light receiving element.

  Further, according to a method of producing a liquid-surface reflection type inclination sensor according to an embodiment of the present invention, the liquid surface formed on a plate that is vertically and infinitely wide with respect to the horizontal liquid surface from the Young-Laplace system and the hydrostatic pressure system. A liquid surface shape calculating step of obtaining a shape in the horizontal direction x and the vertical direction y; an optical simulation step of irradiating a dark field pattern from a temporary light source to obtain a light receiving pattern reflected by a temporary mirror surface having the liquid surface shape; Determine whether the image accuracy of the light receiving pattern satisfies the sensor accuracy requirement, and adjust the shape of the cylindrical container for enclosing the liquid, and perform a container adjusting step, and adjust the cylindrical length to the minimum designed horizontal length. It has a container formed in a shape.

  In the liquid-surface reflection type tilt sensor, a container shape according to the sensor specification can be obtained quickly and at low cost.

FIG. 2 is a configuration diagram of an optical system of a liquid-surface reflection type inclination sensor according to an embodiment. FIG. 2 is a diagram illustrating an example of a dark field pattern in FIG. 1. It is a flowchart which concerns on the design method of the container of the inclination sensor which concerns on embodiment. It is a figure explaining the meniscus shape formed around the infinite vertical plate. It is a figure showing a calculation result of a liquid level shape formed in both side walls. It is a figure which shows the complementation result of the liquid surface shape formed on both side wall surfaces. It is a figure which shows the liquid surface shape formed on both side wall surfaces in each temperature condition. FIG. 3 is a diagram illustrating a virtual optical system assumed in an optical simulation. FIG. 4 is a diagram comparing a received light image obtained by an optical simulation with an actual received light image. It is a figure which shows the difference by the container diameter of a liquid surface shape, (a) is a figure which shows the liquid surface shape of a container diameter of 15 mm, (b) is a figure which shows the liquid surface shape of a container diameter of 20 mm. FIG. 4 is a flowchart showing details of a container adjustment step of FIG. 3. It is a figure which shows the influence on the received light image by the difference of container height. It is a figure showing a calculation result of a liquid surface shape calculation process of an example. It is sectional drawing which shows the example of a form of the container of the inclination sensor formed by the Example, (a) is a figure which shows the example 1 of a form, (b) is a figure which shows the example 2 of a form.

  A preferred embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a configuration diagram of an optical system of a liquid reflection type inclination sensor (hereinafter, simply referred to as an inclination sensor) 1 according to an embodiment. The tilt sensor 1 includes a light source 2, a collimating lens 3, a dark field pattern 4, a polarizing plate 5, a beam splitter 6, a focus lens 7, a λ / 4 plate 8, a liquid 9, a container 10, a light receiving element 11, and an arithmetic processing unit 12. Having.

  As the light source 2, an LED is used, but another light source may be used. The collimating lens 3 emits the light beam from the light source 2 in parallel. The dark field pattern 4 is described in detail in the above-mentioned Patent Document 2, but has a two-dimensional pattern in which a large number of slits 4b are arranged in a black mask portion 4a as shown in FIG. The polarizing plate 5 polarizes the light beam that has passed through the dark field pattern 4 into s-polarized light with respect to the beam splitter 6. The beam splitter 6 has a semi-transmissive surface 6a, and reflects the light flux passing through the polarizing plate 5 upward. The focus lens 7 condenses the light reflected by the beam splitter 6. The λ / 4 plate 8 gives a phase difference to the light beam that has passed through the focus lens 7. The light beam that has passed through the λ / 4 plate 8 enters the liquid 9 sealed in the cylindrical container 10 and is reflected on the surface of the liquid 9 (free liquid surface 9a). The liquid 9 preferably has a small surface tension, a large specific gravity, and a small effect due to a temperature change. For example, a silicon oil, a fluorine-based liquid, or the like is selected. The free liquid surface 9a maintains a horizontal liquid surface with respect to the inclination of the surveying instrument (inclination sensor 1). 1 denotes the height from the bottom surface of the container 10 to the horizontal liquid level when the surveying instrument is horizontal. The symbol h indicates the height of the container 10, and the symbol D indicates the length of the container 10 in a certain horizontal direction passing through the center of the container. The light beam reflected by the free liquid surface 9a again passes through the λ / 4 plate 8, the focus lens 7, and the beam splitter 6, and is received by the light receiving element 11. As the light receiving element 11, an image sensor, a two-dimensional area sensor, or the like is used. The light receiving image (light receiving pattern) obtained by the light receiving element 11 is subjected to image analysis by the arithmetic processing unit 12. The processing unit 12 detects the amount of displacement of the received dark-field pattern 4. For the arithmetic processing unit 12, a CPU or the like is used.

  In the above description, the λ / 4 plate 8 and the polarizing plate 5 are provided to exclude a light beam reflected in an undesired direction, but are optional components. Further, it is permissible to configure the above optical element with another optical element or to add another optical element. The above dark-field pattern 4 is an example, and other patterns such as dots, which are recognizable by image analysis, are acceptable. Further, the dark field pattern 4 may be a one-dimensional barcode, and the light receiving element 11 may be a line sensor. The above arrangement of the optical system is an example. In the above description, the light beam enters from below the liquid 9, but the light beam may enter from above the liquid 9. Further, in the above configuration, the light beam enters from a direction perpendicular to the horizontal liquid surface (horizontal portion) of the free liquid surface 9a, but the light beam enters from a direction inclined with respect to the horizontal liquid surface of the free liquid surface 9a. May be.

  The gist of the present invention relates to adjusting the size of the above-described tilt sensor 1 without actually manufacturing the container 10 and manufacturing the container 10 with the minimum size. The design method described below is realized by a personal computer or the like having at least a CPU, a RAM, a ROM, a keyboard, and a display unit as hardware elements. Various programs for executing each step of the present embodiment are stored in the ROM, and the CPU executes the programs. Various conditions and the like can be input from the keyboard, and a graph of the liquid surface shape, simulation results, calculated values, and the like are output to the display unit.

  FIG. 3 is a flowchart according to a method for designing the container 10 of the tilt sensor 1 according to the embodiment. Details of each step will be described later.

  First, when the design is started, the process proceeds to step S1, where the liquid surface shape when the liquid 9 is sealed in a container 10 having a certain shape is calculated (liquid surface shape calculation step).

  Next, the process proceeds to step S2, where an optical simulation of a light-receiving image that will be obtained by the light-receiving element 11 is performed based on the liquid surface shape calculated in step S1 (optical simulation step).

  Next, the process proceeds to step S3, and it is determined with reference to the result of the optical simulation whether the shape of the container 10 is in an allowable range in light of sensor specifications. If it is within the allowable range (YES), the shape may be determined and the design may be terminated. If it is outside the allowable range (NO), the process proceeds to step S4, the shape of the container 10 is changed, and the process returns to step S1 (container adjustment step). The “container height determination step” of step S5 will be described later.

(Liquid surface shape calculation process)
In the liquid surface shape calculation step, as a first step, a liquid surface shape (meniscus) of a liquid formed on an infinitely wide plate perpendicular to the horizontal liquid surface as shown in FIG. 4 is obtained. This liquid surface shape is derived from the Young Laplace equation and the hydrostatic equation, and is as follows (Makoto Miyazaki, Masami Mizutani, Tadashi Takemoto, Akira Matsunawa, "Analysis of the meniscus shape formed around a cylinder") Journal of the Japan Welding Society, Vol. 15, No. 4, 1997, pp. 674-680). Assuming that the distance in the direction perpendicular to the vertical plate is x, the height of the liquid in the direction of the vertical plate is y, and the angle between the horizontal plane and the curved surface is φ, x and y are [Equation 1] and [Equation 2]. Here, γ is the surface tension of the liquid, and ρ is the density of the liquid. θ indicates the contact angle between the vertical plate and the curved surface. By changing φ, the liquid surface shape from the vertical infinite wall surface can be obtained on the two-dimensional orthogonal coordinates in the horizontal direction x and the vertical direction y. Hereinafter, a curve representing the liquid surface shape formed on the vertical infinite wall surface is referred to as a first curve f1.

  Next, the first curve f1 in the first step is a shape in a state where the infinite vertical plate and the liquid are completely wet (contact angle θ = 0 degree), but actually, the contact angle θ ≠ 0. Can be degrees. In this case, it is preferable to correct. In the second step, the actual contact angle θ1 between the container wall surface and the sealed liquid is obtained, and the y-axis is offset in the x-axis direction until the angle between the first curve f1 and its y-axis becomes the contact angle θ1. (See the y-axis shown by the dashed line in FIG. 4). The actual contact angle θ1 may be obtained by dropping the liquid 9 to be sealed on a material plate on which the container 10 is to be actually formed and actually measuring it (for example, an automatic contact angle meter DMs-601, Phoenix 150, height gauge, etc.). HD-AX).

  Next, while the actual container 10 is cylindrical and has both side walls, what is obtained up to the above process is a liquid surface shape of one side wall surface. Therefore, this is corrected in the third step. FIG. 5 is a diagram showing the result of the calculation, showing the calculation result of the liquid surface shape formed on both side wall surfaces. This will be described with reference to FIG. Through the first and second steps, a first curve f1 for one side wall surface is obtained (FIG. 5 shows a liquid surface tension γ = 20.9 [mN / m] and a liquid density ρ = 965 [kg / m]. ^ 3], the actual contact angle θ1 was made as 0 °). In the third step, the horizontal length of the container 10 is assumed to be 24 mm, and the curve from x = 0 to x = 12 (that is, the assumed horizontal length ÷ 2) of the first curve f1 is obtained. , X = 12 is developed symmetrically, a new X-axis (horizontal axis in FIG. 5) is set with x = 12 as the center of the container (X = 0), and the y-axis of the first curve f1 is set as the container. It is set as a Y-axis (vertical axis in FIG. 5) indicating the liquid level in 10. As a result, a second curve f2 indicating the liquid surface shape on both side walls as shown in FIG. 5 can be obtained.

  Next, in the liquid-surface reflection type tilt sensor, the shape near the center of the container (near X = 0) is important. The liquid surface shape in the third step (FIG. 5) lacks continuity near the center of the container because the liquid surface shape is created by crossing curves from the left and right. Therefore, in the fourth step, the second curve f2 is interpolated by a quadratic function. Techniques for quadratic function interpolation are known. The interpolation is not limited to the quadratic one, and may be performed by a polynomial of cubic, quartic, quintic,..., But quadratic function interpolation is preferable to reduce the load on hardware resources. It was confirmed that sufficient results could be obtained by interpolation. FIG. 6 shows the result of quadratic function interpolation of FIG. FIG. 6 is an enlarged view of the vicinity of the center of the container in FIG. 5. The horizontal axis X is the distance [mm] from the center of the container, and the vertical axis Y is the liquid level [μm]. The solid line indicates the liquid surface shape obtained in the third step, and the broken line indicates the liquid surface shape interpolated in the fourth step. As described above, in the “liquid level shape calculation step”, a curve closer to the actual liquid level shape is obtained by performing the second to fourth steps as necessary based on the first step. Can be.

  FIG. 7 is a diagram showing the liquid surface shape formed from the container wall surface at each temperature condition (−40 ° C., 20 ° C., and 70 ° C.) in the calculation result obtained by the above “liquid level shape calculation step”. is there. The horizontal axis in FIG. 7 indicates the distance [mm] from the center of the container, and the vertical axis indicates the liquid level [mm]. In FIG. 7, assuming that the liquid 9 is a fluorinated liquid, the actual contact angle θ1 is 0 degree, the liquid surface tension γ is 21.00 [mN / m] at −40 ° C., and 16.40 [mN / m] at 20 ° C. m], 12.75 [mN / m] at 70 ° C, liquid density ρ 2000 [kg / m ^ 3] at -40 ° C, 1869 [kg / m ^ 3] at 20 ° C, 1760 [kg] at 70 ° C / m ^ 3], and the horizontal length of the container 10 is assumed to be 15 mm. From FIG. 7, it was confirmed that even when the temperature conditions were changed, the liquid surface shape under each temperature condition could be predicted.

(Optical simulation process)
By the “liquid level shape calculation step”, a two-dimensional liquid level shape in the container 10 can be predicted by the second curve f2. In the optical simulation step, a temporary mirror surface 9a 'is created using the three-dimensional model Z = f (X, Y) of the second curve f2, and a light reception image of the reflected light from the temporary mirror surface 9a' is simulated.

  FIG. 8 shows a virtual optical system assumed in the “optical simulation step”. The light from the light source 2 'is collimated by the collimating lens 3', passes through the dark field pattern 4 ', and is turned by the semi-transmissive surface 6a' toward the temporary mirror surface 9a '. The temporary mirror surface 9a 'simulates a free liquid surface formed when a liquid is sealed in a container 10 having a diameter of φD (see FIG. 8) and a cylindrical shape. The light receiving pattern reflected by the temporary mirror surface 9a 'is acquired by the light receiving element 11'. The center of the light beam of the light source light incident on the temporary mirror surface 9a 'passes through the center O (container center X = 0) of the temporary mirror surface 9a'. The light beam diameter φd of the light source light (see FIG. 8) is an effective range of the liquid surface (a range used for analyzing the received light image), and is set according to the performance of the light receiving element 11. The optical simulation described above can be performed by, for example, ZEMAX (manufactured by ZEMAX Development Corporation). However, the present invention is not limited to this software, and other commercially available optical software may be used.

  FIG. 9 is a diagram comparing the received light image obtained in the “optical simulation step” with the actual received light image. The right column of FIG. 9 is a light-receiving image obtained by actually preparing a circular cylindrical container 10 with a diameter of 15 mm, enclosing a fluorine-based liquid into the container, and measuring the light-receiving image. Note that in this specification, a fluorine-based liquid refers to a solvent (such as an organic solvent) containing fluorine as a constituent element. The left column in FIG. 9 is a light-receiving image obtained by creating the temporary mirror surface 9a 'shown in FIG. 8 with the liquid surface shape shown in FIG. 7 and performing an optical simulation. The upper row is at 20 ° C., the middle row is at −40 ° C., and the lower row is at 70 ° C. From FIG. 9, it can be seen that the simulation result (left column) is very similar to the actual (right column) under each temperature condition.

  Further, it can be seen from the left column of FIG. 9 that the image focused at 20 ° C. is out of focus at −40 ° C. and 70 ° C. In this case, by increasing the diameter φD of the container 10, a change in the liquid surface shape due to a temperature change can be reduced. 10A and 10B are diagrams showing a difference in the liquid surface shape depending on the diameter of the container. FIG. 10A is a diagram showing a liquid surface shape with a container diameter of 15 mm, and FIG. 10B is a diagram showing a liquid surface shape with a container diameter of 20 mm. FIG. 10 is obtained in the “liquid level shape calculation step”. The horizontal axis represents the distance [mm] from the center of the container, and the vertical axis represents the liquid level height in the container [μm]. (A) is an enlarged view of FIG. 7), and is a diagram showing a liquid surface shape near the center of the container when the diameter φD of the container is 15 mm. (B) is a diagram showing a liquid surface shape near the center of the container when only the diameter of the container is changed to φD = 20 mm. By increasing the diameter φD of the container, it can be confirmed that the change in the liquid surface shape due to the temperature change becomes small. From this, the size of the container 10 can be adjusted by performing the “liquid surface shape calculation step” and the “optical simulation step” so that a desired light-receiving image can be obtained. Can be predicted. Hereinafter, the method will be described.

(Container adjustment process)
In the container adjustment step, it is determined from the result of the “optical simulation step” whether the shape of the container 10 is within an allowable range in light of the sensor specifications. This determination is made based on whether or not the numerical value indicating the image accuracy of the light receiving pattern is within a range allowed as a numerical condition satisfying the accuracy required for the sensor. As the numerical value indicating the image accuracy, any one of a contrast value, a numerical value indicating the rising edge of an edge, and the like of the light receiving pattern obtained by the optical software, or a combination thereof is used. As a specific numerical value of the numerical condition satisfying the sensor accuracy, a value selected by those skilled in the art may be used.

  As shown in FIG. 3, if the numerical value indicating the image accuracy is within the allowable range (YES), the size of the container 10 may be determined and the design may be terminated. If it is not within the allowable range (NO), the process moves to step S4, and the size of the container 10 can be changed and adjusted so as to satisfy the sensor specifications. By executing the flow of FIG. A minimum container size can be determined.

  FIG. 11 is a flowchart detailing the step S4 “change container shape” of FIG. In FIG. 11, steps S1 and S2 are as described with reference to FIG. 3, but the value of the light beam diameter φd (see FIG. 8) is fixed, and the diameter φD of the container 10 (see FIG. 8) is temporarily set. Steps S1 and S2 are performed. Next, the process proceeds to step S3, and it is determined whether the numerical value indicating the image accuracy is in an allowable range in light of the sensor specifications. If the numerical value is not within the allowable range (NO), the process proceeds to step S41, the container diameter φD is increased, and the process returns to step S1. If it is within the allowable range (YES), the process proceeds to step S42, where the container diameter φD is reduced, and the process returns to step S1. By repeating this, the minimum diameter φDmin of the container 10 can be determined. As long as the numerical value indicating the image accuracy of the optical simulation is equal, the smaller value of the container diameter φD is determined as optimal.

  Alternatively, the design shown in parentheses in steps S41 and S42 in FIG. 11 can be performed. Space for the inclination sensor 1 may be limited due to space specification limitation in the surveying instrument. That is, when the container diameter φD is limited, the value of the container diameter φD is fixed. Then, the beam diameter φd is provisionally set, and steps S1 and S2 are performed. Next, if the numerical value indicating the image accuracy is not in the allowable range in step S3 (NO), the beam diameter φd is reduced in step S4, and the process returns to step S1. If it is within the allowable range in step S3 (YES), the beam diameter φd is increased, and the process returns to step S1. By repeating this, it is possible to determine the optimum light beam diameter φd when the container diameter φD is limited. It is preferable that the luminous flux diameter φd has the same numerical value indicating the image accuracy, because the accuracy of the light receiving element 11 is relaxed as the value is larger.

  As described above, according to the present embodiment, it is possible to predict a received light image without actually creating the container 10 of the tilt sensor 1, and to provide design feedback based on a simulation result. Further, even if the type and temperature conditions of the liquid 9 to be sealed in the container 10 are changed, the shape of the liquid surface can be predicted, so that the size of the container can be easily adjusted. Further, since the minimum container size can be obtained by repeating the feedback, the time and cost for optimizing the shape of the container 10 can be greatly reduced.

  Further, when the container diameter φD (the length of the container in the horizontal direction) is determined, the optimum height h (see FIG. 1) of the container 10 can also be determined.

  FIG. 12 is a diagram showing the influence on the received light image due to the difference in the container height. FIG. 12 is a light-receiving image measured at a temperature condition of 20 ° C. and −30 ° C. by enclosing a fluorine-based liquid in a cylindrical container 10 having a container diameter φD = 15 mm actually prepared. The right column shows the container height h = 4.6 mm, and the left column shows the container height h = 3.6 mm. In a container having a height of 3.6 mm, when the temperature is low, the liquid 9 comes into contact with the ceiling (lid) of the container, the liquid surface shape changes, and the received light image is blurred. That is, even if the container diameter φD satisfies the sensor specifications, if the container height h is lower than the liquid level height h ′ (see FIG. 1), it will be understood that the result according to the simulation cannot be obtained. In order to avoid this, the container 10 needs a certain height.

  The minimum required value of the container height h can be determined from the maximum value of the liquid level at each temperature obtained in the “liquid level shape calculation step”. For example, when a liquid having the characteristics shown in FIG. 7 is used, the maximum value Ymax of the Y value of the second curve f2 is 1.43 mm. The height must be equal to or greater than the height h 'of the horizontal liquid level plus 1.43 mm. Thus, when the diameter φD of the container 10 is determined, the minimum container height hmin that does not affect the liquid surface shape can be determined by hmin = h ′ + Ymax.

  This “container height designing process” may be performed in the final stage after the optimum container diameter φD (or light beam diameter φd) is determined as step S5 in FIG. Accordingly, the smallest container 10 in the height direction can be designed as the container shape.

(Example)
Examples will be described below. FIG. 13 is a diagram showing a calculation result of the liquid surface shape calculation step of the embodiment. In the example, a fluorine-based liquid was used as the liquid 9. The liquid characteristics are as follows: liquid surface tension γ is 21.00 [mN / m] at −40 ° C., 16.40 [mN / m] at 20 ° C., 12.75 [mN / m] at 70 ° C., and liquid density ρ Is 2000 [kg / m ^ 3] at -40 ° C, 1869 [kg / m ^ 3] at 20 ° C, 1760 [kg / m ^ 3] at 70 ° C, and the capillary constant is 0.014, 20 at -40 ° C. The actual contact angle θ1 was 0.013 at 70 ° C and 0.012 at 70 ° C. The pattern pitch of the dark field pattern 4 was 80 μm, the pattern width was 40 μm, and the luminous flux diameter φd was 2.5 mm. As a result of executing the design method of the present embodiment under this condition, the minimum shape of the container 10 in the present embodiment is, as shown in FIG. 13, the minimum diameter φDmin = 18 mm and the maximum Y value Ymax is −40 ° C. Was 1.46 mm at 20 ° C., 1.33 mm at 20 ° C., and 1.21 mm at 70 ° C., indicating that the minimum container height was hmin = h ′ + 1.46 mm. That is, if the container diameter φD is 18 mm or less, there is no horizontal portion near the center of the container (X = 0), and the accuracy of the tilt sensor 1 deteriorates. When the container diameter φD is 18 mm or more, the inclination sensor 1 becomes large. Regarding the height, when the height h of the container 10 was set to be equal to or less than the height h ′ of the liquid surface +1.46 mm, it was found that the liquid 9 contacted with the container ceiling and the accuracy of the tilt sensor 1 was deteriorated.

  FIG. 14 shows an embodiment of the container 10 of the tilt sensor 1 created based on the results of the above embodiment. FIGS. 14A and 14B are longitudinal sectional views of the container 10, wherein FIG. 14A is a diagram illustrating a first embodiment, and FIG. 14B is a diagram illustrating a second embodiment. The container 10 hermetically seals the liquid 9 with a bottomed oil cylinder 101 having a bottomed circular cylinder and a lid 102 having a circular cylindrical shape. (A) is a form in which the inner peripheral surface of the oil bath 101 and the outer peripheral surface of the lid 102 are adhered and the liquid 9 is sealed, and (b) is the outer peripheral surface of the oil bath 101 and the inner peripheral surface of the lid 102. And the liquid 9 is sealed. The height h ′ of the horizontal liquid level may be 0 or more when the surveying instrument (tilt sensor 1) is tilted to the maximum. For example, if h ′ = 2 mm, the container 10 is a lid in the form of FIG. The inner diameter of the body 102 is 18 mm, and the height of the inner peripheral portion of the lid 102 is 3.46 mm. In the form (b), the inner diameter of the oil bath 101 is 18 mm, and the inner peripheral portion of the oil bath 101 is formed. Is created so that the height of the is 3.46 mm.

  Note that the minimum container height hmin is also preferably prepared by setting the value of Ymax to + (container radius × tan (inclination angle)) in preparation for the container 10 being inclined. Further, it is preferable that the minimum diameter φDmin is created with a margin of + 20% for the value of the minimum diameter φDmin in consideration of the precision of the optical component, the surface accuracy, or the tolerance of the component. For this reason, even if the container 10 is made larger than the minimum designed value in the present embodiment, it is included in the scope of the present invention if the method of the present invention is used.

  Further, a preferred modified example of the present embodiment will be described.

(Modification 1)
In the above, the design method and the preparation method of the regular cylindrical container 10 having the container diameter φD are illustrated, but the method of the present embodiment can be applied to other container shapes. For example, when it is desired to create a square prism-shaped container 10, two-dimensional curves f2 are created in a diagonal direction of the container 10 and a direction orthogonal to two opposing sides of the container 10, and these are combined into a three-dimensional shape. An optical simulation may be performed using the model. When it is desired to create an elliptical cylindrical container 10, second curves f2 may be created in the short axis direction and the long axis direction, respectively, and an optical simulation may be performed using a three-dimensional model obtained by combining these. As described above, if a plurality of second curves f2 are obtained in a certain horizontal direction of the container 10, the liquid surface shape can be predicted even in a polygonal or non-circular container. Based on this, the container 10 can be made in a minimum size.

(Modification 2)
As shown in FIG. 12, even when the container height h is low and the liquid surface touches the ceiling of the lid 102, the liquid surface is formed from the container wall surface (second curve f2) and the ceiling wall surface. By synthesizing the liquid surface shape (first curve f1), the liquid surface shape can be predicted. That is, even if the container height h cannot be increased due to the space specification limitation in the surveying instrument, the container diameter φD can be adjusted by executing the flow of FIG. 3 using this liquid surface shape.

  As described above, the preferred embodiments and modified examples of the present invention have been described. However, it is also possible to combine each form and each modified example based on the knowledge of those skilled in the art, and such forms are included in the scope of the present invention. .

DESCRIPTION OF SYMBOLS 1 Tilt sensor 2 Light source 3 Collimating lens 4 Dark field pattern 6 Beam splitter 7 Focus lens 9 Liquid 9a Free liquid surface 9a 'Temporary mirror surface (virtual free liquid surface)
10 container 11 light receiving element 12 arithmetic processing unit

Claims (7)

From the Young-Laplace equation and the equation of hydrostatic pressure, a liquid surface shape calculation step of calculating the liquid surface shape of the liquid formed on an infinitely wide plate perpendicular to the horizontal liquid surface in the horizontal direction x and the vertical direction y,
An optical simulation step of irradiating a dark field pattern from a temporary light source to obtain a light receiving pattern reflected by a temporary mirror surface having the liquid surface shape,
A container adjustment step of determining whether the image accuracy of the light receiving pattern satisfies a sensor accuracy requirement, and adjusting the shape of a cylindrical container that encloses the liquid,
With
In the liquid surface shape calculation step, a first curve f1 representing the liquid surface shape is obtained from two directions of one wall surface of the container and the other wall surface opposite thereto, and the first curve f1 is determined based on the first curve f1. A second curve f2 indicating the liquid surface shape in the container is obtained, where X is the horizontal distance from the center of the container, and Y is the height of the liquid surface.
In the container adjusting step, the optical simulation step is performed by assuming the length of the container in the X direction while fixing the light beam diameter of the light source light incident on the container, and the image accuracy of the light receiving pattern is determined by the sensor. When the accuracy requirement is satisfied, the length of the container in the X direction is reduced, and when the accuracy requirement is not satisfied, the length of the container in the X direction is increased. A method of designing a container for a liquid level reflection type tilt sensor, wherein the diameter of the container is determined by optimizing a smaller value of the length .
From the Young-Laplace equation and the equation of hydrostatic pressure, a liquid surface shape calculation step of calculating the liquid surface shape of the liquid formed on an infinitely wide plate perpendicular to the horizontal liquid surface in the horizontal direction x and the vertical direction y,
An optical simulation step of irradiating a dark field pattern from a temporary light source to obtain a light receiving pattern reflected by a temporary mirror surface having the liquid surface shape,
A container adjustment step of determining whether the image accuracy of the light receiving pattern satisfies a sensor accuracy requirement, and adjusting the shape of a cylindrical container that encloses the liquid,
With
In the liquid surface shape calculation step, a first curve f1 representing the liquid surface shape is obtained from two directions of one wall surface of the container and the other wall surface opposite thereto, and the first curve f1 is determined based on the first curve f1. A second curve f2 indicating the liquid surface shape in the container is obtained, where X is the horizontal distance from the center of the container, and Y is the height of the liquid surface.
In the container adjusting step, in the container adjusting step, the length of the container in the X direction is fixed, and the optical simulation step is performed assuming a light beam diameter of light source light incident on the container, and the light receiving pattern is formed. When the image accuracy satisfies the sensor accuracy requirement, the light beam diameter is expanded, and when the image accuracy is not satisfied, the light beam diameter is reduced, and this is repeated. design method of the container of the liquid surface reflective inclination sensor you and determining the speed of light diameter.
In the liquid surface shape calculation step, an actual contact angle θ1 of the liquid with respect to the container is obtained, and the y-axis is shifted by x until the angle between the first curve f1 and the y-axis becomes the contact angle θ1. The method for designing a container for a liquid-reflection-type tilt sensor according to claim 1 or 2 , further comprising a step of offsetting in the axial direction .
The container of the liquid level reflection type tilt sensor according to claim 1 or 2 , wherein the liquid level shape calculation step includes a step of complementing a shape near X = 0 of the second curve f2 with a polynomial. Design method.
The maximum value Ymax of the Y value of the second curve f2 is determined, and the height h of the container is designed to be equal to or greater than the value obtained by adding the maximum value Ymax to the height h ′ of the horizontal liquid level of the liquid. The method for designing a container for a liquid-reflection-type tilt sensor according to claim 1, further comprising a design step .
A liquid surface shape calculation step of determining the liquid surface shape of a liquid formed on an infinitely wide plate perpendicular to the horizontal liquid surface in the horizontal direction x and the vertical direction y from the Young-Laplace formula and the hydrostatic pressure formula,
An optical simulation step of irradiating a dark field pattern from a temporary light source to obtain a light receiving pattern reflected by a temporary mirror surface having the liquid surface shape,
It is determined whether the image accuracy of the light receiving pattern satisfies the sensor accuracy requirement, and a container adjusting step of adjusting the shape of the cylindrical container for enclosing the liquid,
In the liquid surface shape calculation step, a first curve f1 representing the liquid surface shape is obtained from two directions of one wall surface of the container and the other wall surface opposite thereto, and the first curve f1 is determined based on the first curve f1. A second curve f2 indicating the liquid surface shape in the container is obtained, where X is the horizontal distance from the center of the container, and Y is the height of the liquid surface.
In the container adjusting step, the optical simulation step is performed by assuming the length of the container in the X direction while fixing the light beam diameter of the light source light incident on the container, and the image accuracy of the light receiving pattern is determined by the sensor. When the accuracy requirement is satisfied, the length of the container in the X direction is reduced, and when the accuracy requirement is not satisfied, the length of the container in the X direction is increased. Determining the diameter of the container with a smaller value of the length being optimal,
A method for producing a liquid level reflection type tilt sensor, wherein a container is produced in a cylindrical shape with a minimum horizontal length.
A liquid surface shape calculation step of determining the liquid surface shape of a liquid formed on an infinitely wide plate perpendicular to the horizontal liquid surface in the horizontal direction x and the vertical direction y from the Young-Laplace formula and the hydrostatic pressure formula,
  An optical simulation step of irradiating a dark field pattern from a temporary light source to obtain a light receiving pattern reflected by a temporary mirror surface having the liquid surface shape,
  It is determined whether the image accuracy of the light receiving pattern satisfies the sensor accuracy requirement, and a container adjusting step of adjusting the shape of the cylindrical container for enclosing the liquid,
In the liquid surface shape calculation step, a first curve f1 representing the liquid surface shape is obtained from two directions of one wall surface of the container and the other wall surface opposite thereto, and the first curve f1 is determined based on the first curve f1. A second curve f2 indicating the liquid surface shape in the container is obtained, where X is the horizontal distance from the center of the container, and Y is the height of the liquid surface.
In the container adjusting step, in the container adjusting step, the length of the container in the X direction is fixed, and the optical simulation step is performed assuming a light beam diameter of light source light incident on the container, and the light receiving pattern is formed. When the image accuracy satisfies the sensor accuracy requirement, the light beam diameter is expanded, and when the image accuracy is not satisfied, the light beam diameter is reduced, and this is repeated, and a larger value of the light speed diameter when the sensor accuracy requirement is satisfied is optimized. Determine the light speed diameter,
A method for producing a liquid-surface reflection type tilt sensor, comprising producing a container in a cylindrical shape with a light speed diameter designed to be the maximum with respect to the length of the container in the X direction.